1. Field of the Invention
The present invention relates generally to a waterproof rubber plug for filling the gap between the outer surface of an electrical wire and the inner surface of a mounting hole of a connector housing.
2. Description of the Prior Art
One of conventional waterproof rubber plugs of this type is disclosed in Japanese Utility Model Laid-Open No. 62-163879.
In this waterproof rubber plug, a connector housing has a mounting hole for engaging a waterproof rubber plug of a substantially cylindrical shape. The waterproof rubber plug also has a through hole which extends along the longitudinal central axis of the waterproof rubber plug for engaging the outer surface of an electrical wire. The waterproof rubber plug comprises a thick-walled body portion for filling the gap between the outer surface of the electrical wire and the inner surface of the mounting hole of the connector housing, and a thin-walled clamped portion extending from an end of the body portion. The waterproof rubber plug is designed to fill the gap between the outer surface of the electrical wire and the inner surface of the mounting hole when it is inserted into the mounting hole of the connector housing.
A pair of inside annularly raised portions are so formed as to project from the inner surface of the through hole of the body portion at regular intervals in the longitudinal direction. The inside annularly raised portions cause the inner surface of the through hole to be a corrugated surface for tightly engaging the outer surface of the electrical wire. In addition, a plurality of outside annularly raised portions are so formed as to project from the outer surface of the body portion at regular intervals in the longitudinal direction. The outside annularly raised portions also cause the outer surface of the body portion to be a corrugated surface for tightly engaging the inner surface of the mounting hole of the connector housing.
The connector housing is designed to receive therein a wire connecting terminal. One end of the terminal is provided with a rubber-plug clamping piece. When the clamped portion of the waterproof rubber plug is clamped by the rubber-plug clamping piece, the waterproof rubber plug is secured to the electrical wire.
A flange portion extends radially from the outer periphery of the end portion of the clamped portion of the waterproof rubber plug. One end of the electrical wire is drawn out of the through hole at the flange portion. The drawn portion of the electrical wire serves as a connecting portion, in which the coating portion of the electrical is removed to expose the conducting portion thereof. The terminal is provided with a wire clamping portion. When the electrical wire is clamped by the wire clamping portion, the conducting portion of the connecting portion is electrically connected to the terminal.
According to such a waterproof rubber plug, it is possible to ensure the waterproof characteristic between the mounting hole of the connector housing and the electrical wire.
However, when a branch electrical wire is connected to a main electrical wire using such a conventional waterproof rubber plug, the coating portion must be stripped at an intermediate portion (a branch connecting portion) of the main electrical wire drawn out of the connector housing. In addition, in order to connect the branch electrical wire to the main electrical wire, both of the exposed conducting portion of the main electrical wire and the conducting portion of the branch electrical wire must be clamped by a joint terminal or the like. Moreover, the connecting portion of the main electrical wire must be clamped by the wire clampling portion of the terminal at another place. That is, two electrical connections must be performed.
In order to ensure the waterproof characteristic at the branch connecting portion, it is required to waterproof the branch connecting portion, for example, by binding a pair of tape-like members round the main and branch electrical wires on both sides of the branch connecting portion and by arranging the branch connecting portion within an insulating cover. The tape-like members must fill in the spaces between the outer surfaces of the main and branch electrical wires and the inner surface of the insulating cover. Such a structure is disclosed in Japanese Patent Laid-Open No. 60-130066.
That is, in such a conventional structure, the clamping and waterproofing of the electrical wires must be performed at two places, respectively. Therefore, there is a problem in that the wire connecting structure and assembly operation thereof are complicated. In addition, since the electrical connections are also performed at two places, there is a problem in that the reliability on the conductivity may be decreased by the electrical connections.